Atmosphere sampling probe



Oct. 15, 1963 F. c. LUXL ATMOSPHERE SAMPLING PROBE Filed Sept. 30, 19 02 Sheets-Sheet l Oct. 15, 1963.- F. c. LUXL ATMOSPHERE SAMPLING PROBE 2Sheets-Sheet 2 Filed Sept. 30, 1,960

United States Patent 3,166,843 ATMUSPHERE SAMPLING PROBE Frank C. Luxl,Bryn Mawr, Pa., assignor to Leeds and Northrup Company, Philadelphia,Pa, a corporation of Pennsylvania Filed Sept. 30, 1960, Ser. No. 59,704Claims. (6i. 73-4215) This invention relates to atmosphere samplingprobes of the type used in gas analysis systems to obtain continuousflow of a sample stream from atmospheres ladened with :dust,contaminants, and water vapor and has for an object the provision offeatures which prevent the clogging of the probe during extended periodsof operation.

The need continuously to analyze the combustion or flue gases offurnaces, such as those employed in power plants, is Well known to thoseskilled in the art. In many instances the composition of the gases,particularly the oxygen content thereof, has been used for both manualand automatic control to assure the operation of the furnaces or similarprocesses at high efiiciency. Because the dust-ladened combustion gasesmay include condensable water vapor which may combine with the dust toform deposits which block the free flow of sample, efforts have beenmade to provide means to prevent the accumulation of solids within or onthe probe to a point where it becomes necessary to shut down theanalyzing system in order to open the flow path for the sample stream.For this purpose, it has been proposed to supply the probe with steam toinduce the flow of a sample stream through the probe. It has also beenproposed to supply the probe with a water spray designed to minimize theaccumulation of solids Within the region of the openings into the probe.While these prior proposals have been helpful, much has been left to bedesired to extend the uninterrupted time during which a sampling streammay be obtained from a furnace atmosphere. More particularly, steamprobes have been found effective in minimizing the clogging of theprobes within the region of the openings for the flow of the samplestream into them. However, steam probes have not been entirelysatisfactory due to corrosion and/ or the accumulation of solids withinthe sampling line in the regions where the temperature of the sampleline has caused condensation of the steam. Probes of the water-spraytype while effective to prevent clogging of the flow channel of theprobe itself, nevertheless produce such reductions of temperature withinthe regions of the access openings into the probe that cementitiousproducts form growing solids on the outside of the probe whicheventually close the openings and thus require shut-down of the systemfor cleaning as indicated above.

In accordance with the present invention, it has been found thatuninterrupted sampling times of a new order of magnitude can be achievedby utilizing high temperature steam to operate an ejector pump forproducing in the region of the access openings to the probe a lowpressure for forced flow of a sample stream into the probe incombination with the introduction down-stream from the access openingsof a stream of wash Water which not only acts to condense the steamabout the solid particles in the sample stream but also insures thepresence of Water in sufiicient quantity to dilute corrosive materialsand maintain all cementitious-forming products in solution. Thus, thecombination of the steam at-the probe inlet or inlets in conjuction withthe stream of wash water introduced within a critical region in theprobe has overcome the difficulties experienced with probes of typesheretofore utilized.

For further objects and advantages of the invention,

reference is to be had to the following detailed description taken inconjunction with the accompanying drawings, in which:

FIG. 1 is an enlarged top view, partly in section, of a probe assemblyembodying the invention;

FIG. 2 is a sectional view (on a larger scale) taken on the line 22 ofFIG. 3;

FIG. 3 is a side elevation of the probe of FIG. 1 together With itsassociated supply lines; and

FIG. 4 is a front view of the probe assembly of FIG. 3 and includes theanalyzing apparatus associated there with.

Referring now to FIG. 1, the invention in its preferred form has beenillustrated as applied to a probe 10 comprising tubular structureincluding a section 11 of diameter materially greater than the diameterof a tube 12, the interior of which provides a flow channel for thesample stream from the atmosphere. The atmosphere is normally that of afurnace, one wall 13 of which has been illustrated as a refractorymaterial which has a metal outer casing 14. A member 15 is welded to thecasing 14 and has threaded thereon one member 16 of a union 17 having athreaded ring 18 and a second threaded member 19. A nipple 20 isthreaded to the member 19 and also has threaded to it a pipe cap 21through which the tubular member 12 extends. Also extending through thecap 21 is a steam supply line 22, the inner end of which is threadedinto a coupling 23 for connection with probe 19. Thus, the probe as awhole is supported from the pipe cap 21 which supports the tubularmember 12 and the steam line 22.

The element 11 is made of larger diameter than the tube 12 in order thatone or more access openings, three of which have been illustrated,namely, the access openings 11a, 11b and 110, can be of enlarged size tocontribute to long-time operation free of clogging. The element 11 alsoforms a housing for the steam-jet ejector pump 24 which delivers throughits conical nozzle an expanding steam-stream. This steam, from steamsupply line 22, produces within the region of the inlet to a dilfuser,shown as a tubular member 25, a region of low pressure. The low pressureso produced by the ejector pump results in forced flow of a samplestream from the furnace atmosphere through the access openings Ila-11cinto the tubular member 25. This member 25 by reason of its venturisection, that is, with gradually increasing diameters from the centralportion to the respective ends thereof, provides a diffusion action forthe sample stream and steam prior to delivery into the tube 12. Thediffusion action results in the thorough mixing of the steam and thesample stream and also provides forced flow of the sample stream throughand outwardly of the tube 12.

By utilizing high temperature steam, there is minimized any reduction oftemperature within the region of the access openings Ila-41c, therebypreventing condensation of components of the sample stream onto theprobe walls adjacent the access openings. The forced flow of the samplestream into the sampling line, including tubes 12 and 25, reduces to aminimum the possibility of clogging. By high temperature steam, I meansteam at a temperature at which condensation does not take place undernormal ope-rating conditions within that part of the probe locatedupstream from the region of introduction of wash water. In thisconnection,.it is to be noted that the steam line 22 is not insulated,but instead, receives heat from the interior of the furnace and to someextent its temperature may be increased by this heating action.

In order to minimize the possibility of a reduction in the temperatureof the sample stream, comprising the mixture of the furnace gases andthe steam prior to adequate dilution with water, it is preferred thatthe wash Water be introduced into the tube 12 at a region within theinterior of the furnace. Thus, a water supply pipe 26 is provided with aplurality of openings 26a adjacent its closed end for producing aplurality of streams of water directed outwardly into the interior oftube 12 at a point not too far removed from the outlet of tube 25, yetnot close enough to produce condensation either in the pump or around oradjacent the access openings. The stream of wash water thoroughly mixeswith the mixture of stem and furnace gases and performs a number offunctions. First, there is initiated condensation of the steam on andabout the dust particles and other foreign matter within the samplestream. The foregoing action in conjunction with a supply of Wash waterin relatively large quantity minimizes the formation of cementitiousproducts and enlarged bodies of solids which if allowed to form wouldtend to clog tube 12 or the sample line. Corrosion is prevented by thediluting action of the wash water in respect to any acid-formingcomponents present in the furnace gases. The overall result is a probeof extended life providing trouble-free operation over indefinitely longperiods of time.

There has been shown in FIG. 3 a pressure gauge 30, a pressure regulator31 and 'a shut-off valve 32 between the wash water line 26 shown only inFIGS. 1 and 2 and the wash water supply line 26s. The sample stream istaken from the sample line 12a in communication with the interior oftube or tubular member 12. A continuation of the steam-supply line 22 isillustrated by the short length of pipe 22b.

The front view of FIG. 4 of the parts just described in FIG. 3 includesa throttling valve 33 for a steam-supply line 22a and the sampling line12a has been illustrated with its connection to a separator 35 having anoutlet pipe 36 connected to an analyzing instrument 37. A pressure gauge38 is provided for the separator 35. The separator 35 is preferably ofthe type illustrated and described in Kraftson et a1. Patent 2,895,335,reference to which should be made for details of interior construction.

For the purposes of the present invention, it is sufficient to say thatthe sample stream tangentially enters the separator 35 and through theresulting centrifugal action within the separator, condensate is causedto flow downwardly of the separator and out an exit pipe 39 and thenceto Waste while a solid-acid-free gas sample fiows outwardly through theline 36 to the analyzer 37. As previously indicated, the analyzer 37frequently includes control apparatus which by reason of any change froma preselected value of the oxygen present in the furnace modifies thefurnace operation in a manner to increase its efiiciency.

It is to be observed that the pressure as read by gauge 38 will bedetermined by the adjustment of the throttling valve 33 and the settingof the pressure regulator 31. As already set forth, the steam-jetejector pump 24 produces forced flow of the sample stream not onlythrough the tube 12 but through the entire system. Thus, through out thesystem there is maintained a positive pressure which prevents in-flow ofgases of any and all kinds except the ingress of the sample streamthrough the openings 110-110 of FIGS. 1 and 2.

From the foregoing it will be seen that the invention broadly includesthe concept of means for introducing steam into the fore end, i.e., thefurnace end, of the sampling structure as by means of the pipe 22connected by coupling 23 to and forming a part of the sampling probe 10.The steam at the delivery point in the modification shown desirably hasa pressure of the order of 40 pounds per square inch, the steam prior toits passage through the throttling valve 33 having a pressure between 70and 100 pounds per square inch, thus insuring the flow of an adequateamount of dry steam into the fore end of the probe 10. Those skilled inthe art will understand the use of the term dry steam to distinguish thesame from so-oalled wet steam, i.e., having present moisture insubstantial percentage. T he steam will ordinarily be at a temperatureupwards of about 340 F. By reason of the flow of steam through or, asillustrated, past the access means in the form of the ports Ila-11c,there is avoided any possibility of a reduction in the temperature ofthe portions of the probe in the region where the sample enters to avalue producing condensation of moisture in the sample and the growth ofcementitious deposits on and about the region of the ports. This is incontrast with prior probes including water sprays which cool the probestructure in the region adjacent the point of entry of sample whichcauses build-up of a balllike mass of cementitious material which thoughnot interrupting the flow of the water into the sample intakeopeningshas nevertheless eventually closed off the openings by encasing theentire end of the probe to prevent flow of the sample stream into theproble.

The present invention includes the provision of the wash water, suppliedat the rate of one to one and one-half gallons per minute, to producerapid cooling at a location to convert the steam into condensate withina region so close to the access ports Ila-11c that the dry steam has notthe opportunity to condense in the zone between the location of thewater jet openings 26a and the access ports 11a11c. On the other hand,the water spray openings 26a. are sufiiciently removed from the ports11a11c that any cooling effect by conduction through the tube 12, orotherwise, does not produce the possibility of condensation of moisturein the sample within the region of the access ports 11a-11c. Inpractice, a spacing of about three inches between openings 26a and thenear end of tube 25 has been found to meet the foregoing requirements.It is to be understood that that spacing does not represent a criticaldimension. The three-inch spacing between openings 11a11c and openings26a has proven satisfactory in a given embodiment of the invention.

With the foregoing features present, the mixture of condensed steam,sample gas including contaminants, and wash-water progress under forcedflow to and through the separator 35 with the cleansed sample streambeing received by the analyzer 37 through the delivery line 36.

For additional technical information set forth not as a limitation butas illustrative of a typical operation, the valve 33 and the pressureregulator 31 were set to produce on the pressure indieater 38 a readingof 3% pounds per square inch gauge. Such a pressure was found adequateto produce through the delivery line 36 a washed and cleansed samplestream of 30 cubic feet per minute where the line 36 was feet in lengthand was made of one-quarter inch outside diameter copper tubing. Forgreater lengths of line, the pressure at the outlet of the separator 35will be increased and for shorter lengths it may be decreased.

It is desired that the steam be supplied at a pressure which may rangebetween seventy and one hundred pounds per square inch gauge and thatthe wash water be supplied at the rate of about one gallon per minute.The pressure from the water supply line 26s should be of the order ofabout 25 pounds per square inch gauge (minimum) and the regulator 31 setwithin the range of between 15 and 20 pounds per square inch gauge.

The foregoing technical details of a typical system including myinvention include a tubular member 12 of one-half inch pipe withopenings Ila-11c of five-eighths inch diameter. The water supply tube 26is one-quarter inch outside diameter, stainless steel, aboutthree-sixteenths inch inside diameter. The steam line 22 is of stainlesssteel pipe. Preferably all the probe parts are of stainless steel.

Now that a preferred embodiment of the invention has been described withparticularity, it is to be noted that modifications thereof may be madewithin the scope of the appended claims. For example, there may beutilized motive means other than that formed by the steam-jet ejectorpump 24. Suction can be applied to the pipe 12 at any point in thesystem and as far down-stream as the analyzer 37. Regardless of wherethe motive means is located, however, it is understood that means suchas the steam line 22 will continue to be used to inject idry steam underpressure into the probe to assure its presence at the point of sampleentry, such as in the region of the access ports 11a11c, and further,that the washwater must be provided as for example by provision of sprayopenings at 26a disposed in a region adjacent to but spaced down-streamfrom the point of sample entrance.

The access means in the form of openings or ports Ila-11c may be ofdiffering structure, as for example, a spiral opening providingrelatively large continuous area for inward flow of the gases into thetube 12. Where the motive means is located down-stream, the pipe 22 maydirect the steam inwardly of an open ended tube.

What is claimed is: c

1. An atmosphere sampling probe comprising elongated tubular structurehaving within a region adapted to be disposed Within a chamber theatmosphere of which is to be sampled one or more relatively large accessopenings for flow into the tubular structure of a sample stream of saidatmosphere, at steam-jet ejector pump disposed within said tubularstructure and having pressurereducing elements within the region of saidaccess openings for producing forced flow of the sample stream into saidtubular structure in mixture with steam supplied to said ejector pump, asteam line connected to said ejector pump for supplying steam theretohaving a high temperature of value which prevents condensation ofmoisture in the region adjacent said access openings, water supply meansfor introducing a stream of water into said tubular structure at aregion down-stream from said ejector pump thereby to condense said steamand to wash said sample, said last named region being disposed withinsaid chamber, and a sample take-off connection from said tubularstructure located downstream of the region in which said stream of wateris introduced into said tubular structure.

2. An atmosphere sampling probe comprising elongated tubular structurehaving Within a region adapted to be disposed within a chamber theatmosphere of which is to be sampled one or more relatively large accessopenings for flow into the tubular structure of a sample stream of saidatmosphere, a steam-jet eject-or pump disposed within said tubularstructure and having pressurereducing elements within the region of saidaccess openings for producing forced how of the sample stream into saidtubular structure in mixture with steam supplied to said ejector pump, asteam line connected to said ejector pump for supplying steam theretohaving a high temperature of value which prevents condensation ofmoisture in the region adjacent said access openings, water supply meansfor introducing a stream of Water into said tubular structure at aregion down-stream from said ejector pump and at a location forintroduction of said stream of water prior to the reduction of thetemperature of said steam and of said sample to the dew point andsufliciently removed from said access openings to prevent cooling andcondensation in said region adjacent said access openings, said regionbeing disposed within said chamber, means for regulating the relativeflow-rates of said streams of Water and steam for producing rapidtransformation of said steam into condensate, and a sample take-offconnection from said tubular structure located down-stream of the regionin which said stream of water is introduced into said tubular structure.

3. An atmosphere sampling probe comprising elongated tubuler structurehaving between its ends and within a region adapted to be disposedWithin a chamber the atmosphere of which is to be sampled one or morerelatively large access openings for flow into the tubular structure ofa sample stream of said atmosphere, a steam-jet ejector pump disposedwithin said tubular structure and having pressure-reducing elements ktheregion of said access openings for producing forced flow of the samplestream into said tubular structure and mixture with steam supplied tosaid ejector pump, means including a steam line connected to saidejector pump for supplying dry steam thereto having a high temperatureof value which prevents condensation of moisture in said sample streamin the region adjacent said access openings, water-supply means forintroducing a stream of water into said tubular structure at a regiondown-stream from said ejector pump and at a location sufficiently nearsaid openings for introduction of said stream of water prior to upstreamreduction of the temperature of said steam and of said sample to a pointwhere condensation of steam can occur in the zone separating saidopenings and said point of entry of said stream of water into saidstructure, said water supply means being positioned in a region in theprobe disposed within said chamber, and a sample take-off connectionfrom said tubular structure located down-stream of the region in whichsaid stream of water is introduced into said tubular structure.

4. An atmosphere sampling proble comprising elongated tubular structurehaving within a region adapted to be disposed within a chamber theatmosphere of which is to be sampled one or more relatively largeopenings for flow into the tubular structure of a sample stream of saidatmosphere, means for supplying under pressure dry steam to said tubularstructure in the region of said one or more openings having a hightemperature of value which prevents condensation of moisture in saidsample stream in said last-named region, motive means connected withsaid tubular structure for producing forced flow of the sample streaminto said tubular structure in mixture with said steam to form a mixtureof said sample stream and of said steam, water-supply means forintroducing under pressure a stream of water into said tubular structureat a region close to but down-stream from said openings and at alocation prior to the reduction of the temperature of said mixture tothe dew point rapidly to condense and dilute said mixture and wash itthrough said tubular structure, said last named region being disposedWithin said chamber, and a sample takeoii connection from said tubularstructure located downstream of the region in which said stream of Wateris in troduced into said tubular structure.

5. An atmosphere sampling probe comprising an elongated tubularstructure forming a portion of a sampling system, said tubular structurehaving a fore-end for disposition within a space from which a sample ofthe atmosphere therein is to be taken and an aft-end having a dischargepassage for location exterior of said space, means for connecting theremaining portion of the sampling system to said discharge passage, asteam-jet ejector pump connected to the fore-end of said tubularstructure, said pump having a steam line connection, said tubularstructure having access means for entry of said sample into said pump,said steam having a high temperature of value which preventscondensation of moisture in the region adjacent said access means; adiffusion tube for discharge of said sample into said fore-end of saidtubular structure, and means for introducing water into the fore-end ofsaid tubular structure close to but down stream from said diifusion tubeand at a location prior to the reduction of the temperature of saidsteam and of said sample to the dew point rapidly to condense the steamand to wash said sample during its continued flow in the samplingsystem.

References Cited in the file of this patent UNITED STATES PATENTS2,685,205 Barnard Aug. 3, 1954 2,895,335 Kraftson et a1. July 21, 19592,934,958 Kingma May 3, 1960 FOREIGN PATENTS 770,692 Great Britain Mar.20, 1957

1. AN ATMOSPHERE SAMPLING PROBE COMPRISING ELONGATED TUBULAR STRUCTUREHAVING WITHIN A REGION ADAPTED TO BE DISPOSED WITHIN A CHAMBER THEATMOSPHERE OF WHICH IS TO BE SAMPLED ONE OR MORE RELATIVELY LARGE ACCESSOPENINGS FOR FLOW INTO THE TUBULAR STRUCTURE OF A SAMPLE STREAM OF SAIDATMOSPHERE, A STEAM-JET EJECTOR PUMP DISPOSED WITHIN SAID TUBULASTRUCTURE AND HAVING PRESSUREREDUCING ELEMENTS WITHIN THE REGION OF SAIDACCESS OPENINGS FOR PRODUCING FORCED FLOW OF THE SAMPLE STREAM INTO SAIDTUBULAR STRUCTURE IN MIXTURE WITH STEAM SUPPLIED TO SAID EJECTOR PUMP, ASTEAM LINE CONNECTED TO SAID EJECTOR PUMP FOR SUPPLYING STEAM THERETOHAVING A HIGH TEMPERATURE OF VALUE WHICH PREVENTS CONDENSATION OFMOISTURE